Two-Speed Transaxle Gearbox For Electric Vehicles

ABSTRACT

A transmission to transfer power from an electric motor to first and second axles of a vehicle includes an input shaft adapted to be driven by the electric motor and a first planetary gear set. A second planetary gear set has a first member driven by the first planetary gear set, a second member restricted from rotation and a third member. A differential assembly has a first side gear adapted to drive the first axle, a second side gear adapted to drive the second axle and a pair of pinion gears meshed with the first and second side gears. A first clutch is operable to drivingly interconnect the first member and the differential assembly. A second clutch is operable to drivingly interconnect the third member and the differential assembly.

BACKGROUND

The present disclosure generally relates to a power transmission devicefor a motor vehicle. More particularly, a two-speed transaxle for anelectric vehicle is disclosed.

Conventional two-speed transaxles may include an input shaft having twohelical driving gears. Input torque is provided to the input shaft thatmay be supported for rotation on tapered roller bearings. Speedselection is achieved by sliding a synchronizer sleeve between twopositions on an intermediate shaft assembly. A drive pinion of a finaldrive gear set may be part of the intermediate shaft assembly. A finaldrive output gear is attached to a bevel and side gear differentialassembly that distributes output torque to left and right wheels of avehicle. While this type of double-reduction gearbox may have functionedsatisfactorily in the past, this design causes relatively large massesto rotate at relatively large speeds. As such, costly balancingprocedures may be required to assure quiet operation over the desiredlife of the product. Furthermore, the known two-speed transaxle requiresthe manufacture and use of the input shaft, the intermediate shaft and adifferential carrier. Each of these components are rotatably supportedby a housing. The costs associated with manufacturing and supportingthese components may become undesirably burdensome. Furthermore, thepreviously known transaxle may weigh more than desired.

SUMMARY

A transmission to transfer power from an electric motor to first andsecond axles of a vehicle includes an input shaft adapted to be drivenby the electric motor and a first planetary gear set. A second planetarygear set has a first member driven by the first planetary gear set, asecond member restricted from rotation and a third member. Adifferential assembly has a first side gear adapted to drive the firstaxle, a second side gear adapted to drive the second axle and a pair ofpinion gears meshed with the first and second side gears. A first clutchis operable to drivingly interconnect the first member and thedifferential assembly. A second clutch is operable to drivinglyinterconnect the third member and the differential assembly.

In another form, a transmission to transfer power from an electric motorto first and second axles of a vehicle includes an input shaft adaptedto be driven by the electric motor. A first planetary gear set has afirst sun gear driven by the input shaft, a first ring gear restrictedfrom rotation and a plurality of first planet gears rotatably supportedon a first carrier and meshed with the first sun gear and first ringgear. A second planetary gear set has a second sun gear driven by thefirst carrier of the first planetary gear set, a second carrierrestricted from rotation, and second and third sets of planetary gearsrotatably supported by the carrier. Each of the second planet gears aremeshed with the second sun gear and one of the third planet gears. Eachof the third planet gears is meshed with the second ring gear. Adifferential assembly has a first side gear adapted to drive the firstaxle, a second side gear adapted to drive the second axle, and a pair ofpinion gears meshed with the first and second side gears. A first clutchis operable to drivingly interconnect the second sun gear and thedifferential assembly. A second clutch is operable to drivinglyinterconnect the second ring gear and the differential assembly.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a stick diagram of a transaxle constructed in accordance withthe teachings of the present disclosure;

FIG. 2 is a fragmentary perspective view of the transaxle depicted inFIG. 1; and

FIG. 3 is a stick diagram depicting another transmission.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

A two-speed transaxle 10 driven by an exemplary electric motor 12 isdepicted in FIGS. 1 and 2. Transaxle 10 includes an input shaft 14 fixedfor rotation with an output shaft 16 of electric motor 12. Transaxle 10is operable to provide drive torque to a first axle shaft 18 and asecond axle shaft 20. First and second axle shaft 18, 20 drive vehiclewheels (not shown). Power is transferred from input shaft 14 through afirst planetary gear set 22, a second planetary gear set 24, one of afirst clutch 26 and a second clutch 28, a sprocket and chain assembly 30and a differential assembly 32.

Planetary gear set 22 is a simple planetary gear set including a sungear 38 fixed for rotation with input shaft 14. A ring gear 40 iscoupled to a housing 42 of transaxle 10 to restrict rotation of ringgear 40. A plurality of planet gears 44 are rotatably supported on acarrier 46. Each planet gear 44 is in meshed driving engagement with sungear 38 and ring gear 40. Input shaft 14 and sun gear 38 are supportedfor rotation within housing 42 by bearings 48. Based on the arrangementpreviously described, planetary gear set 22 acts as a speed reducer withinput being provided to sun gear 38 and output provided by carrier 46.In the embodiment depicted in FIG. 1, it is contemplated that planetarygear set 22 provides a gear reduction ratio of approximately 5.70:1. Itshould be appreciated that other gear reduction ratios may be utilizedwithout departing from the scope of the present disclosure.

Planetary gear set 24 is a complex planetary gear set driven byplanetary gear set 22. In particular, planetary gear set 24 includes asun gear 50 fixed for rotation with carrier 46 of planetary gear set 22.Planetary gear set 24 also includes a ring gear 52, a first set ofplanet gears 54, a second set of planet gears 56 and a carrier 58. Eachof the first and second planet gears 54, 56 are supported for rotationon carrier 58. Each of planet gears 54 are positioned in meshedengagement with sun gear 50. Each of planet gears 56 are positioned inmeshed engagement with ring gear 52 and one planet gear 54. Carrier 58is coupled to housing 42 and restricted from rotation. Planetary gearset 24 is configured as previously described to assure that ring gear 52rotates in the same direction as sun gear 50.

First clutch 26 is selectively operable to drivingly interconnect sungear 50 with sprocket and chain assembly 30. Similarly, second clutch 28is selectively operable to drivingly interconnect ring gear 52 andsprocket and chain assembly 30. Transaxle 10 is configured as atwo-speed power transmission mechanism. As such, transaxle 10 may beoperated in a low range mode, a high range mode or a neutral mode. Thehigh range mode of operation is obtained by actuating first clutch 26and drivingly interconnecting sun gear 50 with sprocket and chainassembly 30. Second clutch 28 is inactive and does transfer torque atthis time. In the high range mode, planetary gear set 24 does notprovide a gear reduction but merely passes torque from planetary gearset 22 therethrough at a direct or 1:1 ratio.

To operate transaxle 10 in the low range mode, first clutch 26 isdeactivated such that no torque is transferred therethrough while secondclutch 28 is activated to transfer torque from ring gear 52 to sprocketand chain assembly 30. In the embodiment depicted in FIG. 1, it iscontemplated that planetary gear set 24 provides a gear reduction ratioof approximately 1.93:1 when transaxle 10 is operated in the low rangemode. The neutral mode is obtained by deactivating both first clutch 26and second clutch 28.

First clutch 26 includes a drum 60 fixed for rotation with sun gear 50.A hub 62 is fixed for rotation with a drive sprocket 63 of sprocket andchain assembly 30. A first set of clutch plates 64 are splined forrotation with drum 60. A second set of clutch plates 66 are splined forrotation with hub 62. First clutch plates 64 are interleaved with secondclutch plates 66 such that an external force applied to the clutch packcauses torque to transfer through first clutch 26.

Second clutch 28 includes a drum 70 fixed for rotation with ring gear52. A hub 72 is fixed for rotation with drive sprocket 63. A first setof clutch plates 74 are splined for common rotation with drum 70. Asecond set of clutch plates 76 are fixed for rotation with hub 72. Firstclutch plates 74 are interleaved with second clutch plates 76. Uponreceipt of an external compressive force, first clutch plates 74 engagesecond clutch plates 76 to cause a torque transfer through second clutch28.

Drive sprocket 63, hub 62 and hub 72 are fixed for rotation with a driveshaft 80 rotatably supported within housing 42 by a bearing 82. A drivensprocket 84 is fixed for rotation with second axle shaft 20. A chain 86drivingly interconnects drive sprocket 63 and driven sprocket 84. In theexample presented in FIG. 1, drive sprocket 63 includes 37 teeth whiledriven sprocket 84 includes 47 teeth to provide a reduction ratio ofapproximately 1.27:1.

Differential assembly 32 includes a first side gear 90 fixed forrotation with first axle shaft 18. A second side gear 92 is fixed forrotation with second axle shaft 20. Pinion gears 94 are rotatablysupported by a carrier 96. Each pinion gears 94 is in driving meshedengagement with first side gear 90 and second side gear 92. Based on thereduction ratios of the various components previously described,transaxle 10 provides a low range gear ratio of approximately 14.00:1and a high range of approximately 7.24:1.

Another transaxle 200 is depicted in FIG. 3. Transaxle 200 issubstantially similar to transaxle 10. Accordingly, like elements willretain their previously introduced reference numerals. Transaxle 200 isarranged to provide drive torque to first axle shaft 18 and second axleshaft 20 as well as transmit drive torque to a secondary drive line viaa propeller shaft 202 and provide a full-time four-wheel drivearrangement. Planetary gear set 22, sprocket and chain assembly 30 anddifferential assembly 32 are substantially the same as previouslydescribed.

A planetary gear set 204 receives torque from carrier 46 of planetarygear set 22. Planetary gear set 204 includes a ring gear 206 fixed forrotation with carrier 46 of planetary gear set 22. A sun gear 208 iscoupled to housing 42 and restricted from rotation. A plurality ofplanet gears 210 are supported for rotation on a carrier 212. Eachplanet gear 210 is in driving meshed engagement with ring gear 206 andsun gear 208. A first clutch 214 selectively drivingly interconnectscarrier 212 and drive sprocket 63. A second clutch 216 selectivelydrivingly interconnects ring gear 206 with drive sprocket 63. It shouldbe appreciated that planetary gear set 204 may be arranged as a simpleplanetary gear set because ring gear 206 rotates in the same directionas carrier 212 when sun gear 208 is restricted from rotation.

First clutch 214 includes a hub 218 fixed for rotation with carrier 212.A drum 220 is fixed for rotation with drive sprocket 63. A first set ofclutch plates 222 are in splined engagement with hub 218. A second setof clutch plates 224 are in splined engagement with hub 220. Torque istransferred across first clutch 214 when a compressive force is appliedto first clutch plates 222 and second clutch plates 224.

Second clutch 216 includes a drum 230 fixed for rotation with ring gear206. A first set of clutch plates 232 are splined to drum 230. A hub 234is fixed for rotation with drive sprocket 63. A second set of clutchplates 236 are splined to hub 234. Torque may be transferred acrosssecond clutch 216 by applying a compressive force to first clutch plates232 and second clutch plates 236.

A speed increasing gear set 240 includes a pinion gear 242 fixed forrotation with drive shaft 80 and a ring gear 244 in meshed engagementwith pinion gear 242. Speed increasing gear set 240 provides drivetorque to the second drive line via propeller shaft 202. Gearset 240 isconfigured as an overdrive or speed increasing gear set to allowpropeller shaft 202 to include a reduced diameter to transfer torque toanother set of driven wheels. The reduced diameter reduces the mass andthe associated challenges related to balancing a larger diameterpropeller shaft. It should be appreciated that speed increasing gear set240 may also be coupled to drive shaft 80 of transaxle 10 to providefour-wheel drive capability.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without departing from the spirit and scope of thedisclosure as defined in the following claims.

1. A transmission to transfer power from an electric motor to first andsecond axles of a vehicle, the transmission comprising: an input shaftadapted to be driven by the electric motor; a first planetary gear set;a second planetary gear set having a first member driven by said firstplanetary gear set, a second member restricted from rotation and a thirdmember; a differential assembly having a first side gear adapted todrive the first axle, a second side gear adapted to drive the secondaxle, and a pair of pinion gears meshed with said first and second sidegears; a first clutch operable to drivingly interconnect said firstmember and said differential assembly; and a second clutch operable todrivingly interconnect said third member and said differential assembly.2. The transmission of claim 1 wherein said first member and said thirdmember of said second planetary gear set rotate in the same direction.3. The transmission of claim 2 wherein said first member of said secondplanetary gear set is a ring gear.
 4. The transmission of claim 3wherein said second member of said second planetary gear set is a sungear.
 5. The transmission of claim 4 wherein said third member of saidsecond planetary is a carrier rotatably supporting planet gears meshedwith said ring gear and said sun gear.
 6. The transmission of claim 5wherein said first planetary gear set includes a sun gear driven by saidinput shaft and a carrier driving said first member of said secondplanetary gear set.
 7. The transmission of claim 1 further including areduction unit being driven by said second planetary gear set anddriving said differential assembly.
 8. The transmission of claim 7wherein said reduction unit includes a drive sprocket selectively drivenby one of said first and second clutches, a driven sprocket and aflexible drive member drivingly interconnecting said drive sprocket andsaid driven sprocket.
 9. The transmission of claim 8 wherein said drivensprocket is fixed for rotation with said second side gear.
 10. Thetransmission of claim 9 wherein said first and second side gears rotateabout a common axis offset and substantially parallel to an axis ofrotation of said input shaft.
 11. The transmission of claim 1 furtherincluding a speed increasing gear set driven by one of said first andsecond clutches, said speed increasing gear set adapted to transmittorque to a third vehicle axle.
 12. The transmission of claim 1 whereinsaid first member of said second planetary gear set is a sun gear drivenby said first planetary gear set.
 13. The transmission of claim 1wherein said second member of said second planetary gear set is acarrier.
 14. The transmission of claim 1 wherein said third member ofsaid second planetary gear set is a ring gear.
 15. A transmission totransfer power from an electric motor to first and second axles of avehicle, the transmission comprising: an input shaft adapted to bedriven by the electric motor; a first planetary gear set having a firstsun gear driven by said input shaft, a first ring gear restricted fromrotation, and a plurality of first planet gears rotatably supported on afirst carrier and meshed with said first sun gear and said first ringgear; a second planetary gear set having a second sun gear driven bysaid first carrier of said first planetary gear set, a second carrierrestricted from rotation, and second and third sets of planet gearsrotatably supported by said second carrier, each of said second planetgears being meshed with said second sun gear and one of said thirdplanet gears, each of said third planet gears being meshed with saidsecond ring gear; a differential assembly having a first side gearadapted to drive the first axle, a second side gear adapted to drive thesecond axle, and a pair of pinion gears meshed with said first andsecond side gears; a first clutch operable to drivingly interconnectsaid second sun gear and said differential assembly; and a second clutchoperable to drivingly interconnect said second ring gear and saiddifferential assembly.
 16. The transmission of claim 15 furtherincluding a reduction unit being driven by said second planetary gearset and driving said differential assembly.
 17. The transmission ofclaim 16 wherein said reduction unit includes a drive sprocketselectively driven by one of said first and second clutches, a drivensprocket and a flexible drive member drivingly interconnecting saiddrive sprocket and said driven sprocket.
 18. The transmission of claim17 wherein said driven sprocket is fixed for rotation with said secondside gear.
 19. The transmission of claim 18 wherein said first andsecond side gears rotate about a common axis offset and substantiallyparallel to an axis of rotation of said input shaft.
 20. Thetransmission of claim 19 wherein said first and second clutches arefriction plate clutches.
 21. The transmission of claim 15 furtherincluding a speed increasing gear set driven by one of said first andsecond clutches, said speed increasing gear set adapted to transmittorque to a third vehicle axle.